This invention relates generally to a method and apparatus for inspecting workpieces in a transfer line.
A typical transfer line for fabricating metal parts in a machining or assembly line process generally includes a number of different kinds of single-purpose or multipurpose machining units arranged at respective machining stations along a transfer path. A transfer mechanism transfers workpieces along the transfer path and positions each of the workpieces at each machining station. This allows each of the machining units to machine each of the workpieces as the workpieces move along the transfer path to an exit end of the transfer line.
For example, U.S. Pat. No. 5,197,172 issued 30 Mar. 1993 to Takagi et al., discloses a metal fabricating transfer line that includes a plurality of different kinds of single-purpose machining units arranged at plural machining stations located along a transfer path. The transfer mechanism of the Takagi et al. system includes a return conveyor or transfer vehicle that transfers workpieces from an exit end of the transfer path, along a return path, to a workpiece unloading station. Takagi et al. also discloses a numerically controlled general-purpose machine tool that is disposed adjacent the return path. The general-purpose machine tool carries out special machinings on certain predetermined ones of the workpieces that the single-purpose machining units are unable to accomplish. However, a metal fabricating transfer line constructed according to the Takagi et al. patent includes no provision for inspecting workpieces.
As another example, the prior art metal fabricating transfer line and inspection apparatus shown schematically at 10 in FIG. 1 of the drawings includes eight stations 12A-12H. At stations 12A through 12D and 12F through 12H, various machining units 14A-14D and 14F-14H perform operations on workpieces that pass through the eight stations 12A-12H along a transfer path 16. For example, machining unit 14A and station 12A could be a machine for milling the top of the workpiece, machining unit 14B at station 12B could be a machine for milling the sides of the workpiece, machining unit 14C at station 12C could be a boring machine, machining unit 14D at station 12D could be a tapping machine, and machining unit 14F at station 12F could be a counter-boring machine, etc.
Station 12E is a workpiece inspection removal station disposed between machining units 14D and 14F along the transfer path 16. The inspection removal station 12E is disposed in this position to allow an operator to remove a workpiece from the transfer path 16 after the machining operations at preceding stations 12A-12D have been completed but before the machining operations at succeeding stations 12F-12H have been completed. The workpiece inspection removal station 12E is designed to allow an operator to gain access to the transfer path 16 and select, remove and inspect any number of workpieces and at any frequency. The presence of the removal station 12E allows an operator to remove, for example, every fifth workpiece 13 that comes down the transfer path 16, one workpiece 13 per hour, or one workpiece 13 a day. The transfer line and inspection apparatus 10 of FIG. 1 also includes a workpiece inspection area 18 remote from the workpiece inspection removal station 12E where an operator takes workpieces for inspection after having retrieved the workpieces from the transfer path 16 at the removal station 12E. However, a workpiece inspection apparatus constructed according to the prior art transfer line system of FIG. 1 will not allow an operator to remove a workpiece 13 for inspection from any other intermediate machining stage along the transfer path 16. Nor will it allow an operator to remove a workpiece 13 without interrupting workpiece flow along the transfer path 16, or without physically removing the workpiece 13 from the transfer path 16 at that stage. The system of FIG. 1 also requires that a removal station be built into the transfer line to allow such access.
The invention is a transfer line apparatus for performing multiple machining operations on a series of workpieces. The apparatus includes a plurality of different kinds of machining units disposed at respective machining stations disposed along a transfer path. A workpiece transporter is configured to move workpieces along the transfer path so as to position each of the workpieces at each of the machining stations. This allows each of the machining units to machine each of the workpieces as the workpieces move along the transfer path.
Unlike the prior art of record, at least one of the machining units is configured to respond to an inspection command by allowing a designated workpiece to pass by the designated machining unit along the transfer path without being machined by the designated machining unit. This allows the workpiece to be inspected in a form unaltered by the designated machining unit.
The invention also includes a method for inspecting workpieces in a transfer line. According to this method one can inspect workpieces in a transfer line by first providing a plurality of different kinds of machining units at respective machining stations disposed along a transfer path. The workpieces are moved along the transfer path so that the workpieces can be machined at each of the machining stations by the corresponding machining units. A workpiece to be inspected is then selected as well as a desired machined state that the selected workpiece is to be in for inspection. The point along the transfer path at which the selected workpiece will be in the desired machined state is then determined. Any remaining succeeding machining units are then prevented from further machining the selected workpiece as the selected workpiece moves long the transfer path to an exit end of the transfer path. The workpiece is then inspected in the desired machined state.
Objects, features and advantages of this invention include the ability to inspect workpieces in the condition the workpieces were in as they left any one of a number of machining units along a transfer path in a transfer line and without having been further machined or otherwise altered by subsequent machining units along the transfer path; the ability to inspect a workpiece in an intermediate machining stage along the transfer path without interrupting workpiece flow along the transfer path, without physically removing the workpiece from the transfer path at that stage and without having to provide a removal station to allow such access; reducing risk to operators by obviating the need to physically enter the transfer line between working machining units to retrieve parts for inspection; requiring fewer stations in any given transfer line by eliminating the need for a separate inspection and removal station; and to allow transfer lines to be accommodated in smaller facilities by allowing the transfer lines to be shorter in length.